2,908 research outputs found
Writing on Fading Paper and Causal Transmitter CSI
A wideband fading channel is considered with causal channel state information
(CSI) at the transmitter and no receiver CSI. A simple orthogonal code with
energy detection rule at the receiver (similar to [6]) is shown to achieve the
capacity of this channel in the limit of large bandwidth. This code transmits
energy only when the channel gain is large enough. In this limit, this capacity
without any receiver CSI is the same as the capacity with full receiver CSI--a
phenomenon also true for dirty paper coding. For Rayleigh fading, this capacity
(per unit time) is proportional to the logarithm of the bandwidth. Our coding
scheme is motivated from the Gel'fand-Pinsker [2,3] coding and dirty paper
coding [4]. Nonetheless, for our case, only causal CSI is required at the
transmitter in contrast with dirty-paper coding and Gel'fand-Pinsker coding,
where non-causal CSI is required.
Then we consider a general discrete channel with i.i.d. states. Each input
has an associated cost and a zero cost input "0" exists. The channel state is
assumed be to be known at the transmitter in a causal manner. Capacity per unit
cost is found for this channel and a simple orthogonal code is shown to achieve
this capacity. Later, a novel orthogonal coding scheme is proposed for the case
of causal transmitter CSI and a condition for equivalence of capacity per unit
cost for causal and non-causal transmitter CSI is derived. Finally, some
connections are made to the case of non-causal transmitter CSI in [8]
Linear Precoding in Cooperative MIMO Cellular Networks with Limited Coordination Clusters
In a cooperative multiple-antenna downlink cellular network, maximization of
a concave function of user rates is considered. A new linear precoding
technique called soft interference nulling (SIN) is proposed, which performs at
least as well as zero-forcing (ZF) beamforming. All base stations share channel
state information, but each user's message is only routed to those that
participate in the user's coordination cluster. SIN precoding is particularly
useful when clusters of limited sizes overlap in the network, in which case
traditional techniques such as dirty paper coding or ZF do not directly apply.
The SIN precoder is computed by solving a sequence of convex optimization
problems. SIN under partial network coordination can outperform ZF under full
network coordination at moderate SNRs. Under overlapping coordination clusters,
SIN precoding achieves considerably higher throughput compared to myopic ZF,
especially when the clusters are large.Comment: 13 pages, 5 figure
Lecture Notes on Network Information Theory
These lecture notes have been converted to a book titled Network Information
Theory published recently by Cambridge University Press. This book provides a
significantly expanded exposition of the material in the lecture notes as well
as problems and bibliographic notes at the end of each chapter. The authors are
currently preparing a set of slides based on the book that will be posted in
the second half of 2012. More information about the book can be found at
http://www.cambridge.org/9781107008731/. The previous (and obsolete) version of
the lecture notes can be found at http://arxiv.org/abs/1001.3404v4/
Asymptotic Estimates in Information Theory with Non-Vanishing Error Probabilities
This monograph presents a unified treatment of single- and multi-user
problems in Shannon's information theory where we depart from the requirement
that the error probability decays asymptotically in the blocklength. Instead,
the error probabilities for various problems are bounded above by a
non-vanishing constant and the spotlight is shone on achievable coding rates as
functions of the growing blocklengths. This represents the study of asymptotic
estimates with non-vanishing error probabilities.
In Part I, after reviewing the fundamentals of information theory, we discuss
Strassen's seminal result for binary hypothesis testing where the type-I error
probability is non-vanishing and the rate of decay of the type-II error
probability with growing number of independent observations is characterized.
In Part II, we use this basic hypothesis testing result to develop second- and
sometimes, even third-order asymptotic expansions for point-to-point
communication. Finally in Part III, we consider network information theory
problems for which the second-order asymptotics are known. These problems
include some classes of channels with random state, the multiple-encoder
distributed lossless source coding (Slepian-Wolf) problem and special cases of
the Gaussian interference and multiple-access channels. Finally, we discuss
avenues for further research.Comment: Further comments welcom
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